How to Draw Logical Conclusions for LSAT Questions - dummies

How to Draw Logical Conclusions for LSAT Questions

By Lisa Zimmer Hatch, Scott A. Hatch, Amy Hackney Blackwell

For the logical reasoning questions that test your ability to draw logical conclusions (or hypotheses), the LSAT gives you a series of premises (the evidence), and you choose an answer that best concludes the information. Questions that ask you to draw conclusions from premises may be worded like this:

  • Which one of the following most accurately expresses the main conclusion of the argument?

  • Which one of the following most accurately expresses the conclusion drawn in the argument?

  • Which one of the following most logically completes the argument?

As you read through the premises, think of a logical conclusion of your own. Then look through the answer choices to see whether one comes close to matching what you’ve thought up.

The key to correctly answering conclusion questions is to look for the answer choice that addresses most of the information contained in the premises. Eliminate any choices that are off-topic or incomplete. A conclusion that addresses only part of the information may be plausible, but it probably isn’t the best answer. For example, consider the following premises:

Five hundred healthy adults were allowed to sleep no more than five hours a night for one month. Half of the group members were allowed 90-minute naps in the afternoon each day; the remaining subjects were allowed no naps.

Throughout the month, the subjects of the experiment were tested to determine the impact of sleep deprivation on their performance of standard tasks. By the end of the month, the group that was not allowed to nap suffered significant declines in performance, while the napping group suffered more moderate declines.

The best conclusion for these premises would have to address the following:

  • The nightly sleep deprivation of healthy adults

  • The allowance for naps for half of the study group

  • The smaller decline in performance of standard tasks for the group that took naps

Any conclusion that fails to address all three points isn’t the best conclusion. For example, the statement “Sleep deprivation causes accumulating declines in performance among healthy adults” wouldn’t be the best conclusion because it fails to address the effect of naps. A better conclusion would be, “Napping helps reduce the declines in performance caused by nightly sleep deprivation among healthy adults.”

You’ll often see more than one plausible conclusion among the answer choices. Your task is to identify the best choice. Don’t fall for the trap of choosing an answer that just restates one of the premises. These choices may entice you because they echo part of the information in the argument, but the best choice must contain an element of each of the pieces of information presented in the question.

The process is pretty simple, really. Try this sample question to see for yourself:

Over the last eight years, the Federal Reserve Bank has raised the prime interest rate by a quarter-point more than ten times. The Bank raises rates when its Board of Governors fears inflation and lowers rates when the economy is slowing down.

Which one of the following is the most logical conclusion for this paragraph?

  • (A)The Federal Reserve should be replaced with regional banks that can respond more quickly to changing economic conditions.

  • (B)The Federal Reserve has raised the prime rate in recent years to try to control

  • (C)The economy has entered a prolonged recession caused by Federal Reserve policies.

  • (D)The monetary policy of the United States is no longer controlled by the Federal Reserve.

  • (E)The Federal Reserve has consistently raised the prime rate over the last several years.

You know from the language that this is a conclusion question, so you don’t have to look for a conclusion in the argument. Just read through the premises and formulate a quick conclusion, something like, “Because the Federal Reserve has raised interest rates many times over the last eight years, it must fear inflation.”

Eliminate answer choices that aren’t relevant or that contain information not presented by the premises. The argument says nothing about regional banks or the termination of the Federal Reserve’s control over U.S. monetary policy, so you can disregard Choices (A) and (D). Then get rid of any choices that don’t take all premises into consideration. Choice (E) just reiterates the first premise, so it’s wrong.

You’re left with Choices (B) and (C), but Choice (C) contradicts information in the premises. The problem says the Federal Reserve responds to the economy, not the other way around, so it’s wrong to say the Federal Reserve causes a recession. Choice (B) is clearly the best answer. It takes into consideration the information that the Federal Reserve has raised rates and that raising rates is its response to inflation.

Be careful to avoid relying on outside knowledge or opinions when answering conclusion questions. You may have studied the Federal Reserve Bank and have opinions about monetary policy. Choices (A), (C), and (D) reflect some possible opinions about the Federal Reserve. Don’t get trapped into choosing an answer just because it supports your opinion.